Erasable diazotype material with vinyl chloride and methyl acrylate copolymer interlayer

ABSTRACT

Written, typed, penciled, printed and other markings on paper and foils can be erased easily by mechanical means by utilizing an improved interlayer between the surface of the base material and the markings. The interlayer includes a copolymer resin of acrylate-vinyl chloride. The provision of such an interlayer is particularly useful for diazotype intermediate prints.

Tinted 81mm atent Muller 1 1 Dec. 2, 1975 {541 ERASABLE DIAZOTYPE MATERIAL WITH 3.027.256 3/1962 Klimkowski ct a]. 96/75 VINYL CHLORIDE AND METHYL 3.370.949 2/1968 Van Groenland 96/75 ACRYLATE COPOLYMER INTERLAYER gf f 4 2 75 l t: Pt Ml1,PtWth' t I 1 or g H or mg FOREIGN PATENTS OR APPLICATIONS 702.294 l/1954 United Kingdom 96/75 1 1 Asslgneel Andrews Paper & Chemlml 6 1.128.837 10/1968 United Kingdom 96/75 Port Washington, NY. 966.258 8/1964 United Kingdom... 96/75 892.882 4/1962 United Kingdom... 96/75 [22] Wed 1973 1.208.821 10/1970 United Kingdom... 96/75 211 App] 349 727 1.268.666 3/1972 United Kingdom 96/75 P 'E. --Ch' 1 [52 us. c1. 96/75; 96/49; 96/85; 2332 2222"; :5: g Kane 96/87 R; 96/91 R; 428/451; 428/500; sumvln'l Kurucz i 428/511; 428/514; 428/515; 428/520 [51] Int. C19... 603C 1/76; 603C l/80; 603C 1/86 [58] Field of Search 96/75, 87 R. 85. 49, 91 R 1 1 ABSTRACT Written. typed. peneiled. printed and other markings 1 Refflences Clted on paper and foils can be erased easily by mechanical UNITED STATES PATENTS means by utilizing an improved interlayer between the 2360216 1O/1944 Fmius 96/85 surface of the base material and the markings. The in- 2 50 374 3 1950 Peterson 9 /75 terlayer includes a copolymer resin of acrylate-vinyl 2,613,149 10/1952 Unkauf 96/75 chloride. The provision of such an interlayer is partic- 2.627.088 2/1953 A s Ct 211. 96/87 R ularly useful for diazotype intermediate prints. 2.805.159 9/1957 Unkauf 96/75 2.875.051 2 1959 De Maria 96/85 6 ClalmS- 4 Drawing Flgures US. Patent Dec. 2, 1975 3,923,518

ERASABLE DIAZOTYPE MATERIAL WITH VINYL CHLORIDE AND METHYL ACRYLATE COPOLYMER INTERLAYER BACKGROUND OF THE INVENTION Diazotypy is a copying process for making copies from translucent originals by exposing them in contact with a diazotype copying sheet to ultraviolet light and by developing the diazotype sheet thereafter with ammonia or a liquid developer. The diazotype process because of its ease and economics has found wide application during the last 40 years and its principles are well described in Light-Sensitive Systems by Jerome Kosar.

Diazotype copying materials are made by applying a light-sensitive diazo coating to the surface of a base, such as foils, opaque paper, or translucent paper, or cloth. The active components of the light-sensitive layer are monomolecular, crystalline, not self-supporting and need a resinous or a fibrous substance as carrier material.

If paper is used as the base material, the diazotype coating penetrates into and disperses in the top layer of the paper and the diazotype print lines of the final copy are well anchored within the fibrous structure of the paper.

Diazo copies in the engineering field are often used for further design work, and it is desirable that corrections of print lines be made easily and not cut noticeably into the paper, thus damaging it for further markings. Corrections have been made in the past through the use of chemical eradicator solutions which destroy the print line through reduction or oxidation of the print dye. However, such chemicals attack also the paper base to a certain degree and leave a cockled and discolored spot that often shows up on reprinting as an undesired marking. Corrections on diazotypes are often required on intermediate diazotype prints, also called reproducibles or second originals. These are diazotypes coated on a translucent base and the print lines are composed of one or more dyes which are opaque to ultraviolet light.

It is obvious that there is a great need for mechanically erasable diazotype intermediates which do not require chemical eradicators for making corrections of the print lines but can be mechanically erased with a rubber eraser without attacking the surface of the base of the diazotype.

As explained above. this cannot be achieved with the conventional diazotype coating procedure which brings the print line forming components into the upper fibrous felt layers of the base paper. A method for producing erasable diazotypes on paper which has been tried consists of lacquering the base first with a film forming cellulose ester solution in an organic solvent and finally overcoating once more with an organic solvent solution of the diazotype compound with or without resins. The choice of the resins and of the solvents is critical, as it is necessary that the top layer enters the cellulosic ester film without penetrating into and being resorbed by the lower layer. Also, the surface should be sufficiently hard and not smear or scratch during processing in the printing equipment. This process is very critical, and it is costly because of the organic solvent coating systems which are necessary and which in turn can pose a pollution problem for the environmental atmosphere.

A common phenomenon of diazotype intermediate prints is the tendency of the developed print dye to migrate in time into the deeper layers of the paper base whenever the paper base has a certain degree of solubility for the azo dyes of the print lines. Accordingly. earlier attempts of using separation layers for erasable diazotypes failed even though the prints were erasable when freshly made but azo dye migration occurred within days or weeks and only partial erasure was possible then with the penetrated part of the print dye appearing as a ghosting" effect. As a matter of fact, certain resins, when used as interlayers dissolve the azo dye in time and accelerate and increase the migration of the azo dye into the paper base. They therefore cause more ghosting upon erasure than if no interlayer is used. The reason for this effect is not fully understood but it is thought that such resin interlaycrs to a certain degree extract certain components from the paper base which show solubility for the azo dyes.

Another shortcoming of earlier attempts to produce easily erasable diazotypes was the lack of water fastness. Easy erasability had been obtained in some attempts but upon wetting and slight manipulation. the entire layer came off with all printed information. In other words, wet rub resistance was insufficient.

SUMMARY OF THE INVENTION It is the object of my invention to overcome the difficulties and disadvantages heretofore encountered in the prior art and to provide an improved, mechanically easily erasable diazotype of good and lasting performance, which is economical to manufacture and does not necessarily require use of volatile organic solvent systems which, when used, can cause environmental problems.

I have found that vinyl chloride-acrylate copolymer resins applied either from aqueous dispersions or from organic solvent solutions easily form a continuous film on a base, and when overcoated with diazotype coating compositions form an effective barrier against migration of diazotype components and azo dyes of finished prints. Also, their adhesion to the base and to the overcoatings is strong enough for satisfactory web rub resistance and to withstand handling and processing of the diazotype material but the layers can be physically easily removed with a common rubber eraser or equivalent without damage to the base.

Also contemplated in my invention herein is the provision for coating a translucent base with a coating preparation containing an acrylate vinyl chloride copolymer. It is then dried and overcoated with a brown line intermediate diazotype coating and dried again. This diazo reproduction material is used to make a diazotype copy by exposing it in contact with a translucent original to ultraviolet light and then to ammonia vapors. A copy is obtained with deep brownlines on a translucent background. Mechanically rubbing with a rubber eraser easily removes the print lines without damaging the translucent base. In a separate test, identical to the one above, except for the omission of the first coating with the vinyl chloride-acrylate copolymer, a copy is obtained from which the print lines can be mechanically removed only under simultaneous destruction of the translucent base. I

Vinyl chloride-acrylate copolymers of my invention are commercially available in the form of aqueous resin dispersions under the name of (GEON LATICES (trade name by B. F. Goodrich Chemical Company) and 3 POLYCO emulsions (by Borden Inc.).

The vinyl chloride-acrylate copolymers with less acrylic components are externally plasticized with dioctyl phthalate or phosphate plasticizers for film forming purposes. Vinyl chloride-acrylate copolymers with increasing acrylic components are internally plasticized" through the copolymer composition and do not require external plastification. Both types of materials are useful when practicing the invention herein.

While the vinyl chloride-acrylate copolymer resins can be applied alone as interlayers, it is often desirable to add other components to the interlayer coating, such as waxes, pigments, spreading and antifoaming agents, in order to control the degree of adhesion. cohesion. ease of erasure and receptivity to the overcoating.

While the main objective of my invention is an easy mechanically erasable diazotype reproduction material, it is obvious that my process is also applicable to other products, such as vellums, typewriter copy sheets, printed forms and any printed material wherever corrections are required.

The base material for easy erasable diazotypes of my invention can be chosen among all conventional bases used for diazotypes, such as, for example, opaque and translucent papers, cloth, films and metal. While in the ease of metal bases and certain films. such as polyester bases, a penetration of the diazo coating into the base cannot take place, an interlayer of my invention is useful because it affects the degree of adhesion of the film forming overcoatings with the diazo components and thus controls ease of erasability. The preferred base material for my invention is, however, transparent or transparentized paper.

The application of the interlayer of vinyl chlorideacrylate copolymer to a suitable base can be made on any type of conventional coating equipment, depending on the form of the coating preparation. A kiss roller coater with air knife or scraper bar coating heads is useful if the vinyl chloride-acrylate copolymer is to be applied from an aqueous dispersion. Kiss rollers with or without wire bar or counter-roller coating heads are also applicable. Diazotype or blueprint coating machines equipped with applicable coating heads are very useful for the interlayer coating, as they also can serve for the consecutive overcoatings with the diazotype layers. The wet coating layers thus applied dry very easily, but they are scratch sensitive by nature and care should be taken that the coating layer does not undergo any scraping action during the drying process and before it is overcoated with the diazotype coatings.

It is well understood that the interlayer of vinyl chloride-acrylate copolymer can be overcoated with as many overcoatings as is deemed useful for the particular application. Thus for diazotype papers more than one precoat may be applied if desirable.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a greatly enlarged fragmentary view partially in section, with various coating layers broken away, of a diazo reproduction material of the invention herein;

FIG. 2 is a view similar to FIG. 1, however, the base sheet is depicted as being coated on both sides thereof;

FIG. 3 is a view similar to FIG. 1 in which only two layers are employed and without a diazo sensitized layer; and

4 FIG. 4 is a view similar to the embodiment of FIG. 3 except that both surfaces of the base sheet are coated with only two layers.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the embodiment of FIG. 1, a diazo reproduction 10 is depicted fully developed in indicia l2 and lines 14 are formed in the developed diazo sensitized layer 16. A suitable support base sheet 18, which may be formed from any of the base sheets used for diazotypes, is coated on its upper surface with interlayer 20. Interlayer 20 is applied in the form of a resin dispersion or emulsionv As previously indicated, interlayer 20 is formed of vinyl chloride acrylate copolymer and may have been applied in the form of an aqueous dispersion or emulsion and may contain other components as discussed above to modify the characteristics of interlayer 20.

Positioned between interlayer 20 and diazo sensitized layer 16 is precoat layer 22 which is applied over the interlayer 20 and is erasable therefrom whenever any of the indicia formed in the diazo layer requires erasure without destruction of the interlayer or the upper surface of the base sheet 18. Precoat layer 22 may be any one of the conventional precoat compositions employed for making diazotype materials.

A backcoating 24 is applied tothe lower surface of base sheet 18 to prevent curling of the coated base sheet after the drying operation.

In the cut-away section of FIG. 1 indicia 12 is depicted as being erased. The erased indicia 26 illustrates the condition of the various layers, that is, the interlayer 20, the precoat layer 22 and the diazo layer 16 after the indicia has been erased. The erased indicia 26 is rubbed away and shows as a cavity 28 extending through the diazo sensitized layer 16 and into the precoat layer 22 but the interlayer is undisturbed. It should be noted that in practice the diazo sensitized layer and precoat layer are bonded sufficiently so that there is no rubbing off or flaking off. As shown in FIG. 1, indicia l2 and lines 14 are shown extending into the precoat layer. Also, there is sufficient bonding between base sheet 18 and interlayer 20 to prevent wet rub off during initial processing and also during reprocessing after a new indicia has been added to replace the erased indicia at 26. Since erased indicia 26 do not penetrate into the upper surface of base sheet 18 there is no ghosting as would occur if interlayer 22 were not present.

In FIG. 2 there is illustrated a diazo reproduction 10' in which the upper surface is formed having applied thereto an interlayer 20', a precoat layer 22 and a diazo sensitized layer 16' such as is described in FIG. 1. However, in place of the backcoating layer 24, base sheet 18' has applied to the lower surface thereof the same coatings as were applied to the top surface, that is, diazo sensitized layer 16, a precoat layer 22 and an interlayer 20 as shown in FIG. 2. This permits the use of the diazo sheet on either side, thus, there could be a diazo print formed in the back side of base sheet 18' as depicted in the front side thereof.

In FIG, 3 there is depicted an erasable sheet material such as could be used as a drawing paper or as a transparency or as typewriter stock material in accordance with the invention herein. A suitable base sheet 18'', for example, the transparentized base paper or bond paper useful as typewriter or writing paper is coated on one of its surfaces with interlayer 20" which is similar in composition to the layer 20 and 20' of FIGS. 1 and 2. After the base sheet 18" is dried the precoat layer 22", which is similar to the precoat layer 22 and 22' of FIGS. 1 and 2 is applied over interlayer 20". The sheet of FIG. 3 is found to have good receptivity for pencil and ink and easily erases with a mechanical eraser without damage to the base sheet.

In FIG. 4 the coated sheet of FIG. 3 is further coated on its other surface with identical layers used in FIG. 3. Thus the coated sheet of FIG. 4 comprises a base sheet 18", interlayers 20" and precoat layers 22".

Having described the principles of the invention herein the following examples are given by way of illustration only.

EXAMPLE NO. 1

A 100% rag natural paper of 50 g/m basis weight is transparentized according to the process of my copending U.S. Pat. application No. 165,692 by reacting a polyol derivative with a material selected from the class consisting of poly N-methylol derivatives of a polyamino compound and a highly translucent paper of a basis weight of 58 g/m is obtained. This transparentized paper is coated and dried in a single pass on a blueprint coating machine equipped with a kiss rollerscraper bar coating head and a hot air convection dryer with the following preparation:

(1) Interlayer 15,000 ml water 300 g non-colloidal silica* 35 g antifoaming agent 15,000 ml Polyco 2610 (55% aqueous dispersion of vinyl chloride methyl acrylate copolymer; containing 70% to 90% polyvinyl chloride and to 30% methyl acrylate externally plastieized; with -40 parts of preemulsified dioctylphthalate made by Borden, Inc.)

5 g methyl violet After coating and drying, the paper is wound up and the roll can be warehoused or transferred immediately to a diazotype coating machine equipped with three conventional air knife coating stations for precoating, diazo coating, and backcoating, and with high velocity hot air convection dryers after each coating station. The paper is consecutively coated and dried in this machine so that the precoat and the diazo coat are applied to the side which has received the undercoat of the vinyl chloride-acrylate copolymer resin, and then the lower surface is backcoated and dried.

The paper having the interlayer applied thereto was further coated as indicated above with the following coating preparations:

(2) Precoating 90,000 ml water 300 ml ammonia 8,000 g non-colloidal silica* 1,000 g Polyvinyl alcohol 7.500 ml vinylacetate copolymer (50% aqueous dispersion) 1,500 ml mineral wax (50% aqueous dispersion) 100 ml antifoaming agent -continued 5,000 ml glycerine (3) Diazo Coating 90,000 ml water 3,000 g tartaric acid 1,500 g boric acid 6,500 g Diazo No. 88 2,000 g thiourea 1,000 g 4-chlor0resorcinol 2,500 g Coupler RX*** 500 g Coupler RG**** 1,000 ml lsopropanol. 1,500 g Zinc Chloride 1,500 g non-colloidal silica* 5,000 ml polyvinylacetate (50% aqueous dispersion) (4) Backcoating 90,000 ml water 3,000 g urea 2,000 g non-colloidal siliea* 6,000 ml vinylaeetate: copolymer (50% aqueous dispersion) Such as PIGMENT 27105, trade name of Andrews Paper 84 Chemical C0,, lnc.

l-Diazo-3Methyl-4- Beta Resorcylie Alpha-Resnrcy The finished treated paper is used to make a contact copy from a translucent master in a commercial diazotype copying machine, and a print with deep brownlines on a translucent background is obtained. The treated paper processed through the developing machine of the copier without difficulties and the surface did not smear. The obtained copy is well suited to serve as a second original to make further copies.

Print lines were found to erase easily by rubbing with a rubber eraser or with an erasing machine, without damaging the translucent base sheet; correction or alteration can be made if desired and reprints can be made from the corrected copy without ghost marks in the erased areas.

EXAMPLE NO. 2

EXAMPLE NO. 3

A rag natural paper of 53 g/m basis weight was impregnated with a 40% solution of styrene dimer in toluene and dried. A translucent base paper sheet is formed and its basis weight rose to 60 g/m This paper was then treated the same way as in Examples No. l and No. 2 and very similar results were obtained regarding erasability.

EXAMPLE NO. 4

An opaque diazo base paper of chemically pure highly bleached Kraft pulp was coated and dried in sequence with the following preparations:

(1) lnterlayer water Geon 460X2 (50-56% aqueous dispersion of internally plasticized vinyl chloride- -continued Such as Flosspowder. trade name of Andrews Paper 8L Chemical C0,. lnc. Such as sold under the trade name of PlGMENT by ical Co. Inc.

Andrews Paper & Chem- Trade name of Andrews Paper 84 Chemical Co. Inc. for l-diazn-4-dicthyl amino benzene chloride. zinc chloride double salt.

Trade name of Andrews Paper 84 Chemical C(L, Inc. for 2.3-dihydroxy naphthalene-6-sulfonic acid. sodium salt.

The diazo coated sheet was used to make a diazotype copy from a translucent original in a commercial diazotype copying machine. A copy with deep blueprint lines on a white background was obtained. The print lines were easily erasable with a rubber eraser without damage to the paper base.

EXAMPLE NO. 5

Example No. 4 was repeated in all its details with the exception of omitting the l Interlayer. The copy obtained from Example No. 5 looked very similar to the copy obtained from Example No. 4, but the erasure test failed. The print lines could not be removed with a rubber eraser or with an erasing machine without destroying the base paper.

EXAMPLE NO. 6

3 g 550 ml water non-colloidal silica* antifoaming agent polyvinylacetate aqueous dispersion) Geon 576 (a aqueous dispersion of vinyl chloride-acrylate copolymer made by B. F. Goodrich Chemical Co.) Such as 27l0S. trade name of Andrews Paper & Chemical Co.. Inc.

L300 ml After coating and drying, the paper is overcoated on 6 both sides in the same coating machine with a preparation of the following composition:

50 ml 200 ml The thus overcoated and dried base paper sheet is found to have good receptivity for pencil and ink and easily erases with a mechanical eraser without damage to the base sheet.

EXAMPLE NO. 7

A bond paper from chemical pulp of g/m basis weight is coated on both sides on a coating machine equipped with a size press and a Tenter dryer with a coating preparation of the following composition:

l,500 ml water 40 g non-colloidal silica* 3 g antifoaming agent 750 ml polyvinylacetate (50% aqueous dispersion) FPC 7358 (55% aqueous dispersion of vinyl chloride-acrylate copolymer of vinyl chloride and l57c methyl acrylate based on the weight of the resin and after the word plasticized insert the phrase with 25 parts of dioctylphthalate externally plasticized; made by Firestone Plastics Co.) 200 ml Glycerine Such as 27105, trade name of Andrews Paper & Chemical Co.. Inc.

L500 ml After coating and drying, the paper is slit and cut into sheet sizes to fit commercial typewriters.

The coated paper sheet surface is receptive to the ink from the typewriter ribbon and to the carbon from carbon interleaves when used in a commercial typewriter. The printed characters are easily erased with a mechanical eraser without damaging the base paper.

It is apparent that the several objects of the invention as set forth above have been accomplished. It is obvious also that numerous changes in processing of the base sheet and modifications of the formulations can be made without departing from the spirit of the invention defined herein.

What is claimed:

1. An erasable diazotype reproduction material comprising:

a base sheet having applied thereto at least three layers coated on at least one side of said base sheet with at least one of said layers forming an interlayer containing an externally plasticized vinyl chloridemethyl acrylate copolymer wherein from 70% to 3. The erasable diazotype reproduction material of claim 1 wherein said base sheet is a transparentized base sheet.

4. The erasable diazotype reproduction material of claim 1 wherein said other surface of said base sheet has applied thereto a backcoating to prevent curling of the base sheet during processing.

5. The material of claim 1 wherein the copolymer is externally plasticized with diocty'lphthalate.

6. The reproduction material of claim 1 wherein said diazo component containing layer is applied from an aqueous mixture of said diazo sensitive components. 

1. AN ERASABLE DIAZOTYPE REPRODUCTION MATERIAL COMPRISING: A BASE SHEET HAVING APPLIED THERETO AT LEAST THREE LAYERS COATED ON AT LEAST ONE SIDE OF SAID BASE SHEET WITH AT LEAST ONE OF SAID LAYERS FORMING AN INTERLAYER CNTAINING AN EXTERNALLY PLASTICIZED VINYL CHLORIDE-METHYL ACRYLATE COPOLMER WHEREIN FORM 70% TO 90% OF THE COPOLYMER IS POLYVINYL CHLORIDE AND THE BALANCE IS MADE UP OF METHYL ACRYLATE RADICALS, AT LEAST ONE OF SAID LAYERS CONTAINING DIAZO SENSITIZED COMPONENTS WHICH COMPRISES A PHTOSENSITIVE DIAZONIUM SALT, AN ACID STABILIZER AND A DIAZO-COUPLER AND AT LEAST ONE OF SAID LAYERS BEING A PRECOAT LAYER POSITIONED BETWEEN SAID DIAZO COMPONENTS CONTAINING LAYER AND SAID INTERLAYER; WHEREBY THE DIAZO REPRODUCTION IS EASILY ERASED BY MECHANICAL MEANS WITHOUT DESTROYING THE SURFACE OF THE BASE SHEET.
 2. The erasable diazotype reproduction material of claim 1 wherein said base sheet is paper.
 3. The erasable diazotype reproduction material of claim 1 wherein said base sheet is a transparentized base sheet.
 4. The erasable diazotype reproduction material of claim 1 wherein said other surface of said base sheet has applied thereto a backcoating to prevent curling of the base sheet during processing.
 5. The material of claim 1 wherein the copolymer is externally plasticized with dioctylphthalate.
 6. The reproduction material of claim 1 wherein said diazo component containing layer is applied from an aqueous mixture of said diazo sensitive components. 